Expandable sheath and methods of using the same

ABSTRACT

Disclosed herein are expandable introducer sheaths and methods of making and using the same. The sheaths minimize trauma to a patient&#39;s vasculature by allowing for temporary expansion of a portion of the sheath to accommodate passage of a delivery system for an implant, then return to a non-expanded state after the passage of the device. The sheath includes a foldable inner member having a detached flap structure at its distal tip that facilitates expansion of the sheath lumen to increased diameters, and an elastomeric distal end that reduces push and retrieval forces therethrough. The sheath can include a hemostasis seal on its proximal end to prevent the leakage of blood out of the sheath and prevent ballooning of outer layer of the sheath.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/522,986, filed Jun. 21, 2017, which is incorporated by reference inits entirety for all purposes.

FIELD

The present application concerns embodiments of a sheath for use withcatheter-based technologies to introduce a prosthetic device, such as aheart valve or other implant, into the patient's vasculature.

BACKGROUND

Endovascular delivery catheter assemblies are used to implant prostheticdevices, such as a prosthetic heart valve, at locations inside the bodythat are not readily accessible by surgery or where access withoutinvasive surgery is desirable. For example, aortic, mitral, tricuspid,and/or pulmonary prosthetic valves can be delivered to a treatment siteusing minimally invasive surgical techniques, including transcatheterdelivery methods.

An introducer sheath can be used to safely introduce a deliveryapparatus into a patient's vasculature (e.g., the femoral artery). Anintroducer sheath generally has an elongated sleeve that is insertedinto the vasculature and a housing that contains one or more sealingvalves that allow a delivery apparatus to be placed in fluidcommunication with the vasculature with minimal blood loss. Aconventional introducer sheath typically requires a tubular loader to beinserted through the seals in the housing to provide an unobstructedpath through the housing for the prosthetic implant, such as a heartvalve mounted on a balloon catheter. A conventional loader extends fromthe proximal end of the introducer sheath, and therefore decreases theavailable working length of the delivery apparatus that can be insertedthrough the sheath and into the body.

Conventional methods of accessing a vessel, such as a femoral artery,prior to introducing the delivery system include dilating the vesselusing multiple dilators or sheaths that progressively increase indiameter. This repeated insertion and vessel dilation can increase theamount of time the procedure takes, as well as the risk of damage to thevessel.

Radially expanding intravascular sheaths reduce the overall profile ofthe sheath to reduce risk of damage to the vessel. Such sheaths tend tohave complex mechanisms, such as ratcheting mechanisms that maintain theshaft or sheath in an expanded configuration once a device with a largerdiameter than the sheath's original diameter is introduced.

However, delivery and/or removal of prosthetic devices and othermaterial to or from a patient still poses a risk to the patient.Furthermore, accessing the vessel remains a challenge due to therelatively large profile of the delivery system that can causelongitudinal and radial tearing of the vessel during insertion. Thedelivery system can additionally dislodge calcified plaque within thevessels, posing an additional risk of clots caused by the dislodgedplaque. The addition of radially expanding properties can also hinder apractitioner's ability to push the sheath without it bending or kinking.Thus, there remains a need for further improvements in introducersheaths for endovascular systems used for implanting heart valves andother prosthetic devices.

SUMMARY

Disclosed herein are expandable introducer sheaths and methods of makingand using the same. The expandable introducer sheaths disclosed hereinare used to deliver a prosthetic device through a patient's vasculatureto a procedure site within the body. The sheath is constructed to behighly expandable and collapsible in the circumferential direction,while also minimizing the wall thickness of the sheath to minimize theprofile of the delivery system. In addition, the sheath disclosed hereinincludes a distal tip assembly that benefits from use of a flap insteadof a folding configuration to reduce the layers of the tip while at thesame time allowing for enhanced expansion diameters of 30% or more forpassing implants. The flap assembly in the distal tip also allowsenhanced ease of expansion for balloon and implant retrieval. Furtherdisclosed herein is a proximally located seal for mediating leakage ofblood between the outer elastomeric layer and inner folding layer. Theseal's proximal location reduces the layers, bumps and asymmetries atthe tip and the seal is preferably marked for positioning at or near theentry into the patient's vasculature to mediate ballooning or leaks.Also, the seal assembly can include an outer jacket to enhancevisibility of the seal location and guard against ballooning adjacentthe seal.

Some embodiments include an expandable sheath having an elongated innermember and an elastomeric outer member. The elongated inner memberdefines a central lumen and first and second circumferential portions.The first circumferential portion includes first and second longitudinaledges. The second circumferential portion extends between the first andsecond longitudinal edges. The elongated inner member is configured tocrease at the first and second longitudinal edges into a foldedconfiguration. The second circumferential portion, in the foldedconfiguration, is positioned at least partially between the overlappingedges. The outer elastomeric member extends around the elongated innermember and is configured to bias the elongated inner member into thefolded configuration. The elongated inner member also includes a distaltip. The distal tip includes a flap extending from the firstlongitudinal edge at least to the second longitudinal edge in an open(or at least partially unfolded) configuration of the elongated innermember.

In other embodiments, the flap is configured to slide circumferentiallyover an outer surface of the first circumferential portion when theelongated member is biased into the folded configuration by the elasticmember. The second circumferential portion can have a distal edgeextending longitudinally at least to a proximal edge of the flap. Theproximal edge of the flap can extend over the distal edge of the secondcircumferential portion onto an outer surface of the secondcircumferential portion.

The flap in another embodiment can include a longitudinal section of thesecond circumferential portion cut along the second longitudinal edge.The longitudinal section can also be cut circumferentially from thedistal end of the second circumferential portion.

In other embodiments, the expandable sheath can also include an overlapextension. The overlap extension, for example, can extendcircumferentially from the longitudinal section. Also the overlapextension can extend proximally from the longitudinal section.

In other embodiments, the distal tip can further include an elastomericend extending from a distal end of the elongated inner member. Theelastomeric end can include a distally tapering shape. Also, the distaltip can include a marker embedded therein, such as in the inner member.

Also disclosed is a method of making a distal tip of an expandablesheath. The method includes forming a folded configuration in anelongated inner member by forming a crease along a first longitudinaledge and a second longitudinal edge of the elongated inner member. Thefirst circumferential portion is positioned at least partially betweenthe longitudinal edges in the folded configuration. Also, the methodincludes forming a flap on a distal tip of an inner member so that theflap extends from a first longitudinal edge of the inner member at leastto a second longitudinal edge of the inner member. Further, the methodcan include covering the elongated inner member with an elastomericouter member.

The method can include other embodiments, such as extending the flapcircumferentially over an outer surface of the first circumferentialportion when forming the flap. Forming the flap can also include forminga proximal edge on the flap that extends over a distal edge and onto anouter surface of the second circumferential portion. The flap can alsobe formed at least partially by cutting a longitudinal section from thesecond circumferential portion. And, the flap can be formed, at leastpartially, by attaching an overlap extension to the longitudinalsection.

The method can also include attaching an elastomeric end to a distal endof the elongated inner member. And, the method can include forming atapered shape into the elastomeric end.

In other embodiments, a method of delivering a prosthetic device, suchas heart valve, is disclosed. The method can include positioning anexpandable sheath within the vascular system of the patient. And, themethod includes introducing a prosthetic device through the lumen of theexpandable sheath such that the prosthetic device exerts a radiallyoutward force on an inner surface of an inner member of the expandablesheath and locally unfolds the inner member into an expandedconfiguration. The method also includes advancing the prosthetic devicefurther through the lumen to a distal tip of the expandable sheath andcausing a free end of a flap of the distal tip to slidecircumferentially over an outer surface of a first circumferentialportion of the expandable sheath to locally enlarge the lumen inresponse to radial pressure exerted by passage of the prosthetic device.The inner member can, in another aspect, be collapsed at the distal tipafter the prosthetic device passes out of the lumen.

In other embodiments, the method can include advancing the prostheticdevice through an elastomeric end extending around a distal end of thelumen to expand the elastomeric end and at least partially collapsingthe elastomeric end after passage of the prosthetic device therethrough.

In other embodiments, the method can include at least partiallycollapsing the inner member by sliding the free end of the flap of thedistal tip circumferentially over the outer surface of the firstcircumferential portion to locally reduce the diameter of the lumen.

Another embodiment includes an expandable sheath with a proximal seal.For example, the expandable sheath can include an elongated innermember, an elastomeric outer member and the proximal seal. The elongatedinner member includes at least one foldable axial portion The outerelastomeric member extends at least partially over the inner member andis configured to exert a compressive force onto the inner member to biasthe at least one foldable axial portion into a folded configuration. Theproximal seal includes a middle member extending from an outer surfaceof the inner member to an inner surface of the outer elastomeric member.Advantageously, the seal is configured to guard against proximalmigration of fluid from a distal free end of the expandable sheath to aproximal end of the expandable sheath.

In other embodiments, the inner member and outer elastomeric member canhave an unconnected length distal to the proximal seal. For example, theunconnected length can extend distally from the proximal seal to thefree distal end of the expandable sheath. And, the seal is thus blockingleaks by blocking a path starting at the distal free end and extendingproximally along the unconnected length.

In yet other embodiments, the expandable sheath can include an outerjacket extending over the outer elastomeric member at the proximalseal's location. And, the outer elastomeric member can be fused to theinner member at the seal. The outer elastomeric member can also befoldable at the proximal seal, along with the inner member. Distal tothe seal, the inner member can still be foldable independent of theouter elastomeric member. The elongated inner member—in either or bothinstances—can still be configured to at least partially unfold to anopen configuration for passage of an implant.

In other embodiments, the elongated inner member defines a centrallumen, a first circumferential portion including first and secondlongitudinal edges, and a second circumferential portion extendingbetween the first and second longitudinal edges. And, the elongatedinner member can be configured to crease at the first and secondlongitudinal edges into the folded configuration wherein the secondcircumferential portion is positioned at least partially between theoverlapping longitudinal edges.

In other embodiments, the elongated inner member can include a distaltip, the distal tip including a flap extending from the firstlongitudinal edge and at least to the second longitudinal edge in anopen configuration of the elongated inner member.

In other embodiments, the expandable sheath can include a proximallypositioned strain relief portion. And, the proximal seal has a proximalend adjacent a distal end of the strain relief portion. The strainrelief portion can have a length, for example, that is at least 9.5 cmlong.

In other embodiments, a method or process of making an expandable sheathwith a proximal valve is disclosed. The method includes forming a foldedconfiguration in an elongated inner member. For example, forming acrease along a first longitudinal edge and a second longitudinal edge ofthe elongated inner member so that a first circumferential portion ispositioned at least partially between the longitudinal edges in thefolded configuration. Then, covering the elongated member with anelastomeric outer member. Also, the method can include forming aproximal seal proximal a distal free end of the expandable sheath byextending a middle member from an outer surface of the inner member toan inner surface of the elastomeric outer member.

The method can further include blocking a path, extending from a distalfree end and between the inner and outer members, with the proximal sealso as to block leaks. And, fusing the elastomeric outer member to theinner member at the seal.

Fusing for example can include extending an outer jacket over the outerelastomeric member at the proximal seal. And, the method can includestretching the inner and elastomeric outer members over a mandrel intoan open configuration before fusing.

Other embodiments include a method of delivering a prosthetic device.The method includes positioning an expandable sheath within the vascularsystem of a patient up to a proximal seal on the expandable sheath. And,further, introducing a prosthetic device into a lumen of the expandablesheath. The method can also include blocking a leak path starting atdistal free end of the expandable sheath with the proximal seal. Themethod also includes advancing the prosthetic device through the lumenof the expandable sheath such that the prosthetic device exerts aradially outward force on an inner surface of an inner member of theexpandable sheath and locally unfolds the inner member into an expandedconfiguration. Then, the method of delivering includes at leastpartially collapsing the inner member at the distal tip after theprosthetic device has passed out of the lumen of the expandable sheath.

In other embodiments, the method includes at least partially blockingthe path with the proximal seal using a middle layer extending betweenthe inner member and an outer elastomeric member.

DESCRIPTION OF DRAWINGS

FIGS. 1A-1C show side elevation views of an expandable introducer sheath(FIG. 1C) and a delivery apparatus for deployment through the sheath(FIGS. 1A-1B);

FIG. 2 shows a perspective view of an expandable introducer sheath;

FIG. 3 shows a cross-sectional view of a distal tip of an expandableintroducer sheath;

FIG. 4 shows a step in a manufacturing process of an introducer sheathincluding cutting a flap (sheath shown in expanded configuration);

FIG. 5 shows another step of a manufacturing process of the introducersheath including folding the sheath into a folded configuration andcutting a gap into its tip;

FIG. 6 shows another step of a manufacturing process of an introducersheath including attaching an extension of the flap (sheath shown infolded configuration);

FIG. 7 shows an extended overlap for attachment to a cut flap, such asthe cut flap shown in FIG. 4;

FIG. 8 shows another step of a manufacturing process includingattachment of a bilayer strip to a foldable inner member;

FIG. 9 shows another step of a manufacturing process including sealingthe tip and an outer member of the expandable introducer sheathtogether;

FIG. 10 is an end view of overlapping inner member and flap portions ofthe expandable introducer sheath without an elastomeric free endattached;

FIG. 11 is a perspective view of a sheath distal tip without an outermember and prior to bonding of the elastomeric free end;

FIG. 12 is a side elevation view of a profile of a distal tip of anexpandable introducer sheath in a folded configuration on a mandrel;

FIG. 13 is an enlarged view of a leading edge of the sheath shown inFIG. 12;

FIG. 14 is a schematic of an expandable introducer sheath with aproximally positioned seal;

FIG. 15 is a cross-sectional view of an extruded inner member with afoldable thin wall portion;

FIG. 16 is a cross-sectional view of the inner member of FIG. 15 in afolded configuration;

FIG. 17 is a cross-sectional view of the expandable introducer sheathwith foldable inner and elastomeric outer members;

FIG. 18 is a cross-sectional view of an unfolded or expanded introducersheath on a mandrel;

FIG. 19 shows is a cross-sectional view of an unfolded or expandedintroducer sheath wherein the inner and outer members are bondedtogether;

FIG. 20 is a cross-sectional view of the introducer sheath of FIG. 19 ina folded configuration;

FIG. 21 is a cross-sectional view of the introducer sheath of FIG. 20including an outer jacket; and

FIGS. 22A and 22B are schematics of an expandable introducer sheath witha proximal valve being withdrawn from a patient.

DETAILED DESCRIPTION

The following description of certain examples of the inventive conceptsshould not be used to limit the scope of the claims. Other examples,features, aspects, embodiments, and advantages will become apparent tothose skilled in the art from the following description. As will berealized, the device and/or methods are capable of other different andobvious aspects, all without departing from the spirit of the inventiveconcepts. Accordingly, the drawings and descriptions should be regardedas illustrative in nature and not restrictive.

For purposes of this description, certain aspects, advantages, and novelfeatures of the embodiments of this disclosure are described herein. Thedescribed methods, systems, and apparatus should not be construed aslimiting in any way. Instead, the present disclosure is directed towardall novel and nonobvious features and aspects of the various disclosedembodiments, alone and in various combinations and sub-combinations withone another. The disclosed methods, systems, and apparatus are notlimited to any specific aspect, feature, or combination thereof, nor dothe disclosed methods, systems, and apparatus require that any one ormore specific advantages be present or problems be solved.

Features, integers, characteristics, compounds, chemical moieties, orgroups described in conjunction with a particular aspect, embodiment orexample of the invention are to be understood to be applicable to anyother aspect, embodiment or example described herein unless incompatibletherewith. All of the features disclosed in this specification(including any accompanying claims, abstract, and drawings), and/or allof the steps of any method or process so disclosed, may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. The invention is notrestricted to the details of any foregoing embodiments. The inventionextends to any novel one, or any novel combination, of the featuresdisclosed in this specification (including any accompanying claims,abstract, and drawings), or to any novel one, or any novel combination,of the steps of any method or process so disclosed.

It should be appreciated that any patent, publication, or otherdisclosure material, in whole or in part, that is said to beincorporated by reference herein is incorporated herein only to theextent that the incorporated material does not conflict with existingdefinitions, statements, or other disclosure material set forth in thisdisclosure. As such, and to the extent necessary, the disclosure asexplicitly set forth herein supersedes any conflicting materialincorporated herein by reference. Any material, or portion thereof, thatis said to be incorporated by reference herein, but which conflicts withexisting definitions, statements, or other disclosure material set forthherein will only be incorporated to the extent that no conflict arisesbetween that incorporated material and the existing disclosure material.

As used in the specification and the appended claims, the singular forms“a,” “an” and “the” include plural referents unless the context clearlydictates otherwise. Ranges may be expressed herein as from “about” oneparticular value, and/or to “about” another particular value. When sucha range is expressed, another aspect includes from the one particularvalue and/or to the other particular value. Similarly, when values areexpressed as approximations, by use of the antecedent “about,” it willbe understood that the particular value forms another aspect. It will befurther understood that the endpoints of each of the ranges aresignificant both in relation to the other endpoint, and independently ofthe other endpoint.

“Optional” or “optionally” means that the subsequently described eventor circumstance may or may not occur, and that the description includesinstances where said event or circumstance occurs and instances where itdoes not.

Throughout the description and claims of this specification, the word“comprise” and variations of the word, such as “comprising” and“comprises,” means “including but not limited to,” and is not intendedto exclude, for example, other additives, components, integers or steps.“Exemplary” means “an example of” and is not intended to convey anindication of a preferred or ideal aspect. “Such as” is not used in arestrictive sense, but for explanatory purposes.

The terms “proximal” and “distal” as used herein refer to regions of asheath, catheter, or delivery assembly. “Proximal” means that regionclosest to handle of the device, while “distal” means that regionfarthest away from the handle of the device.

The term “tube” or “tubular” as used herein is not meant to limit shapesto circular cross-sections. Instead, tube or tubular can refer to anyelongate structure with a closed-cross section and lumen extendingaxially therethrough. A tube may also have some selectively locatedslits or openings therein—although it still will provide enough of aclosed structure to contain other components within its lumen(s).

The expandable introducer sheath disclosed herein is used to deliver aprosthetic device into a patient's body, through a patient'svasculature, and to a procedure site within the body. The sheath isconstructed to be highly expandable and collapsible in thecircumferential direction, while also minimizing the wall thickness ofthe sheath to minimize the profile of the delivery system. In addition,the sheath disclosed herein includes a distal tip assembly that benefitsfrom use of a “flap” instead of a folding configuration to reduce thetip's layers to two or three while at the same time allowing forenhanced expansion diameters of 30% or more for passing implants. Theflap assembly in the distal tip also allows enhanced ease of expansionfor balloon and implant retrieval back through the expandable sheath.Further disclosed herein is a proximally located seal for mediatingleakage of blood between the outer elastomeric layer and inner foldinglayer at the distal tip (blood that is between the layers due to thefree edges of the flap). The seal's proximal location reduces thelayers, bumps and asymmetries at the distal tip of the sheath and theseal is preferably marked for positioning at or near the site of entryinto the patient's vasculature to mediate ballooning or leaks. Also, theseal assembly can include an outer jacket to enhance visibility of theseal location and guard against ballooning adjacent the seal.

FIGS. 1A-1C illustrate an expandable sheath 10 according to the presentdisclosure and a representative delivery apparatus 110 for delivering aprosthetic implant, such as a prosthetic heart valve, to a patient. Itshould be understood that the delivery apparatus 110 described herein isexemplary only, and that other similar delivery systems can of course beused with the expandable sheath 10. The delivery apparatus 110illustrated herein generally includes a steerable guide catheter 114 anda balloon catheter 116 extending through the guide catheter 114.

The guide catheter 114 and the balloon catheter 116 illustrated in FIGS.1A-1B are adapted to slide longitudinally relative to each other tofacilitate delivery and positioning of prosthetic heart valve at animplantation site in a patient's body, as described in detail below. Theguide catheter 114 includes a handle portion 120 and an elongated guidetube, or shaft, 122 extending from handle portion 120 (FIG. 1B).

FIG. 1C illustrates an expandable sheath 10 that is used to introducethe delivery apparatus 110 and the prosthetic device into the patient'sbody. The expandable sheath 10 has generally tubular configurationdefining a central lumen to guide passage of the delivery system for theprosthetic heart valve. At a proximal end, the expandable sheath 10includes a hemostasis valve that prevents leakage of pressurized blood.Generally, during use a distal end of the sheath 10 is passed throughthe skin of the patient and the sheath 10 is inserted into a vessel,such as the femoral artery. The delivery apparatus 110 (with itsimplant) is then inserted into the sheath 10 through the hemostasisvalve, and advanced through the patient's vasculature where the implantis delivered and implanted within the patient.

In one embodiment, the sheath 10 includes an elongate inner member 20and an outer elastomeric member 50 extending along a common centrallongitudinal axis, as shown in FIG. 2. FIG. 3 shows a cross-sectionalview of a distal tip of the expandable sheath 10, and FIG. 4 shows aside view of the same distal tip in a circumferentially expanded stateduring a manufacturing step. As shown in FIG. 4, the elongate innermember 20 includes a first circumferential portion 24 demarcated from asecond circumferential portion 26 by a pair of folds or creases 22. Thecreases 22 facilitate folding of the elongate member into a foldedconfiguration. In one embodiment, a flap 30 can be cut from the secondcircumferential portion 26 of the inner member 20 by the followingprocedure. Crease 22 (corresponding to edge 38 of the secondcircumferential portion 26) is cut axially to create free edge 46 offlap 30. A second cut is applied generally perpendicular to free edge 46(in a circumferential direction) to form the proximal edge 44 of flap30. This second cut simultaneously forms distal edge 58 of the secondcircumferential portion 26. At this point, the flap 30 comprises a cutportion of the second circumferential portion 26 that includes a distaledge 42, a proximal edge 44, and a free edge 46.

The distal tip's 28 structure and its flap 30 allow for a reducedprofile over prior art devices with built up tips. But, also, the flap30 can promote expandability because the flap 30 is free to slide alongthe outside of the first circumferential portion 24. In someembodiments, the flap 30 is extended proximally and circumferentiallyusing an extended overlap portion 60 that extends the reach of the flap30 allowing for its greater movement relative the first circumferentialportion 24. Such an extended overlap portion is shown alone in FIG. 7and attached to the sheath 10 in FIGS. 6 and 8, and will be discussed indetail below. In another embodiment, the flap 30 can include aradiopaque marker band 52 that is applied to, embedded, or otherwisecoupled to the flap 30 for the purpose of locating the distal tip of thesheath 10 inside the patient's body using radiography.

Although embodiments of the distal tip structure and proximal seal ofthe present invention are shown as part of a sheath with an innerfolding member and an elastic outer member, other types of expandableintroducer sheaths can benefit from such improvements. For example,commonly assigned U.S. patent applications Ser. Nos. 14/880,109 (the'109 application entitled Expandable Sheath); Ser. No. 14/880,111 (the'111 application entitled Expandable Sheath with Elastomeric CrossSectional Portions) and Ser. No. 62/449,454 (the '454 applicationentitled Expandable Sheath), which are hereby entirely incorporatedherein by reference, disclose expandable introducer sheaths that canbenefit from embodiments of the present invention.

In the disclosed embodiments, the sheath 10 can include an outerelastomeric member 50 encasing at least part of the length of expandablesheath 10. An example outer elastomeric member 50 is illustrated inFIGS. 1C and 2. The outer elastomeric member 50 can be formed from avariety of elastomeric materials including polyether ether ketone(PEEK), polyethylene terephthalate (PET), polyphenylene sulfide (PPS),and composite materials reinforced by carbon or glass fibers.Preferably, the outer elastomeric member 50 will be formed ofbiocompatible, anti-clotting materials.

When extending around the outside of the sheath 10, the outerelastomeric member 50 provides an inwardly directed radial force thatserves as a fixation mechanism to prevent longitudinal slippage betweenthe various layers of the expandable sheath 10. The compressive forceprovided by the outer elastomeric member 50 can also facilitate themovement of the circumferential portions of the sheath 24, 26 backtoward the central longitudinal axis of the sheath 10 after theirexpansion by a passing prosthetic device. The sheath 10 is thereforeconstructed to allow for local expansion of the sheath 10 while theimplant is present and then the return of the sheath 10 to its smaller,non-expanded diameter after the implant has passed through. Finally, theouter elastomeric member 50 creates a smooth surface that can minimizedamage to the vascular system as the sheath 10 is being positioned andduring insertion of the delivery system and implant through the sheath10. It is contemplated that a simular inner elastomeric member (notshown) can be included extending through the central lumen of the sheath10 to protect a passing prosthetic device from damage by the sheath 10and to reduce friction between the sheath 10 and the device during itspassage.

Embodiments of the present invention are not limited to the particularelastomeric member illustrated herein. For example, the '109, '111 and'454 applications incorporated herein by reference disclose otherstructure, materials and configurations for the outer elastomeric member50. Also, although the illustrated embodiment of the outer elastomericmember 50 has a circular cross-sectional shape, other shapes arepossible, such as ovals, squares and mixed or irregular shapes definingsome full or partial lumen which the implant delivery device can beextended. Further, the terms “circumferential” or “circumference” or“tube” or “tubular” as used herein are not limited to circularcross-sections and instead extend to full or partial perimeters ofshapes defining full or partial lumens for other layers or passage ofthe implants.

FIG. 15 shows a cross-section of inner member 20 in an expandedconfiguration illustrating the circular cross-section of the innermember 20 including the first and second circumferential portions 24,26. FIG. 16 provides a cross section of the inner member 20 in thefolded configuration, illustrating the circumferential portions 24, 26separated from each other by a pair of fold lines or creases 22. Thecreases 22 extend longitudinally along most of the length of the innermember 20 (as shown in FIG. 4 and discussed above). For example, thefirst circumferential portion 24 includes a first longitudinal edge 36and a second longitudinal edge 38 formed by or extending along thecreases or fold lines 22. The second circumferential portion 26 has itsown longitudinal edges 40 formed by the same fold lines 22 because, atleast in the illustrated embodiment, it completes the perimeter of theinner member 20.

The fold lines 22 need not be straight or continuous along the length ofthe inner member 20. The fold lines 22 can terminate for example at ornear an expanded strain relief portion for connection to the hub at theproximal end of the sheath 10. Also, the distal tip structure caninclude removal or modification of such fold lines. The fold lines 22are formed in the illustrated embodiment by a reduction in wallthickness between the first and second circumferential portions 24, 26.The fold lines 22 could also be formed by scoring, conditioning,composition changes and the like to facilitate compression of the innermember 20 into a compressed, folded configuration, as shown in FIG. 16,before and after passage of an enlarging implant.

In one embodiment, the first circumferential portion 24 occupies a muchgreater proportion of the circular arc or perimeter of inner member 20.For example, as shown in FIG. 15, the first circumferential portion ismore than three-quarters (270 degrees) of the circular cross-section ofthe inner member 20. The second circumferential portion 26, conversely,occupies about one-quarter or less of the remaining circumference of theinner member 20. The proportions of the first and second circumferentialportions 24, 26 can be varied to fit a desired amount of reduction inthe profile of the inner member 20 and remaining sheath 10. Generally,however, the illustrated proportions work well for balancing enough ofthe thicker first circumferential portion 24 for push strength of thesheath 10 and the amount of profile reduction afforded by the thinnersecond circumferential portion 26 to deliver stent-mounted heart valvesand other prosthetic implants.

As shown in FIGS. 16 and 17, the inner member 20 has a foldedconfiguration wherein the first longitudinal edge 36 of the firstcircumferential portion 24 overlaps the second longitudinal edge 38. Inparticular, the creases 22 facilitate—due, for example, to the urging ofthe elastomeric properties of the outer elastomeric member 50—foldingthe elongate inner member 20 into an overlapping configuration. In theoverlapping configuration the longitudinal edges 36, 38 (along thecreases 22) of the first circumferential portion 24 come together andpass each other into the overlapping arrangement. This arrangement alsotraps or enfolds portions or all of the second circumferential portion26 between the overlapping edges of the first circumferential portion 24so as to reduce the profile of the expandable introducer sheath 10.

The inner member 20 is preferably constructed of a tube of relatively(compared to the outer elastomeric member 50) stiff material such as astiff polymer like high density polyethylene (HDPE) or an equivalentpolymer. Integral construction, such as integral extrusion, of the wallportions advantageously avoids the leakage of prior-art sheaths that usea split in the sheath to promote expandability. Also, although theembodiment of the outer elastomeric member 50 shown in the figures has acircular cross-sectional shape, other shapes are possible, such asovals, squares and mixed or irregular shapes as long as some form oflumen is formed through which the implant delivery device can be passed.The '109, '111 and '454 applications incorporated herein by referencedisclose other structure, materials and configurations for the elongateinner member 20 that can be used with the expandable sheath disclosedherein.

As shown in FIGS. 3-6, 9, and 11, the distal tip 28 of the expandablesheath in one embodiment includes the flap 30 extending a short lengthalong the distal end of the expandable sheath 10 and ending atelastomeric free end 54. FIG. 4 shows inner member 20 in an expandedstate during a manufacturing step. The illustrated flap 30 startsgenerally at its connected edge 48, which is located adjacent to firstlongitudinal edge 36 of the first circumferential portion 24. Flap 30extends circumferentially in the direction of the second longitudinaledge 38, as shown for example in FIG. 4. As shown in FIG. 5, when sheathis folded the flap 30 extends over the second longitudinal edge 38 andback onto an outer surface of the first circumferential portion 24.Generally, the amount of overlap beyond the longitudinal edge 38 isdetermined by the maximum profile of the implant and delivery system.

The flap 30 includes a distal edge 42, proximal edge 44 and a free edge46 extending between the distal and proximal edges 42, 44. A top orconnected edge 48 is formed where the flap transitions, or is attached,to the first circumferential portion 24. These four edges are generallystraight and connected at right angles to form a generally rectangularshape for the flap 30 (with some rounding for the corners in someembodiments). Generally, the flap 30 promotes expandability of thedistal tip 28 because the flap 30 is free to slide along the outsidesurface of the first circumferential portion 24. As shown in FIGS.10-11, the distal edge 42, proximal edge 44 and free edge 46 are free toslide or move with expansion and compression (folding) of the innermember 20.

The construction of the distal tip 28 advantageously avoids the need forthe buildup of multiple layers used in conventional tip structures. Forexample, only three layers are included at the flap region of the distaltip 28, including the elastomeric outer elastomeric member 50, the flap30, and an underlying one of the first or second circumferentialportions 24, 26 of the inner member 20. In one embodiment, the flap 30has an axial length along the free edge 46 of about 23±5 mm and acircumferential length at the distal and proximal edges 42, 44 of about12±2 mm.

Flaps 30 of the present invention could have varied shapes anddimensions, such as square, semi-circular or other irregular shapes aslong as some portion of the flap 30 extends sufficiently far axiallyand/or in the circumferential direction to achieve some level of overlapwith the first circumferential portion 24 in at least the compressedcondition. Flaps 30 can take many forms, such as a cut portion of anotherwise closed perimeter shape that is capable of temporary expansionto allow passage of implants. Or, as shown above, flaps 30 can comprisecombinations of materials assembled to give different degrees ofextension or overlap so as to provide the distal tip 28 with improvedexpandability but guard against catching when reassuming a nonexpandedor compressed configuration. The flaps 30 need not be associated onlywith folding sheaths, although is particularly advantageous whencombined with the folding sheath disclosed herein and a valve assemblyas disclosed herein to guard against fluid leaks.

The elastomeric free end 54 of the distal end 28 of the expandablesheath 10 preferably has an annular or tubular shape that is attachedto, and extends distally from, a distal end of the first circumferentialportion 24, as shown in FIG. 9, and tapers in a distal direction. Unlikethe flap 30, which is free to slide, the free end 54 has sufficientelastomeric properties that it stretches to create a lumen sufficientlylarge for passage of the implant. Because of its annular shape, the freeend 54 restrains somewhat the free expansion of the flap 30 relative tothe remainder of the inner member 20. Thus, the annular shape of thefree end 54 can guard against the flap 30 becoming so far displaced thatits return cannot be accomplished by the outer elastomeric member 50alone. The elastomeric free end 54 can be constructed of any elastomericmaterial with sufficient elasticity and fatigue resistance to manageexpansion to the unfolded diameter of the sheath 10 and return. Oneexample of such material is NEUSoft™ thermoplastic polyurethane. Asshown in FIG. 9, the elastomeric free end 54 can also include a portionof the outer elastomeric member 50 bonded to an annularly configuredbi-layer of NEUSoft™ and shaped into a taper at its distal end.

As shown in FIGS. 3-9, the expandable introducer sheath 10 can beconstructed using a process of sectioning the inner member 20, forming astructure for the flap 30 as described above, and then bonding variouslayers together to form the distal tip 28. A radiopaque marker band 52can be applied, adhered or tacked onto the inner member 20 near itsdistal end. Furthermore, as shown in FIGS. 9 and 11, a bilayer strip 62formed from layers 64, 66 can be tacked to the distal edge of the innermember 20 to form part of the elastomeric free end 54. The bilayer strip62 has a circumferential length that is the same as the circumferentiallength of the first circumferential portion 24. Thus, the bilayer strip62 does not form a complete tubular layer in the expanded configuration(as demonstrated in FIG. 11). A pair of longitudinally extending freeedges 82 of the bilayer strip 62 are brought together in the foldedconfiguration and are bonded to each other with the distal end of theouter elastomeric member 50 to form the approximately annularelastomeric free end 54 (as shown in FIG. 9). The free edges 82 are thentrimmed to create a gap 84 that flares slightly extending in the distaldirection.

FIG. 8 shows in cross-section that the bilayer strip 62 has an outerlayer 64 that is positioned outside and extends distally past an innerlayer 66. Both layers 64, 66 are positioned flush with each other at theproximal edge of the bilayer strip 62. The proximal edge of the bilayerstrip 62 is heat tacked onto the distal end of the inner member 20 andthe flap 30. The outer layer 64 can be thinner but longer in the axialdirection than the inner layer 66. The outer layer 64, for example, canbe 0.007 inch thick and 6 mm long. The inner layer 66, for example, canbe 0.012 inch thick and 3 mm long. Stacked together, the total thicknessof the bilayer strip 62 is slightly larger (by 0.002 inch) than thedistal end of the (0.012 inch thick) first circumferential portion 24and the 0.005 inch thick overlapping flap 30. The inner surface of theinner layer 66 and the first circumferential portion 24 are preferablyflush with each other for a smooth inner lumen.

As an additional improvement, an extended overlap portion 60, such asthe one shown in FIG. 7, can be attached to the cut flap 30. Theextended overlap 60 has a rectangular body 68, a small tab 70 and alarge tab 72 formed of a material the same or similar to the innermember 20, such as high-density polyethylene (HDPE). In one embodiment,the rectangular body 68 is approximately 11 mm by 23 mm and includes aproximal rounded corner 74. The small tab 70 extends circumferentiallyfrom the rectangular body and includes a proximal rounded corner 74. Thesmall tab 70 has a rectangular shape and extends 3 mm in thecircumferential direction from the circumferential edge of therectangular body 68 and 5 mm in the longitudinal direction. The largetab 72 also extends circumferentially from the rectangular body 68. Thelarge tab 72 has a rectangular shape and extends 12 mm in thecircumferential direction and has an axial length of 7 mm. As a whole,then, the extended overlap 60 has a U-like shape with a long arm (thelarge tab 72) and a short arm (the small tab 70) that is configured toengage and extend the rectangular outside edges of the flap 30 cut fromthe second circumferential portion 26.

As shown in FIG. 6, the extended overlap 60 is attached (for example, byheat tacking) to the flap 30 cut from the second circumferential portion26 to form a composite flap 30. The large tab 72 and rectangular body 68are layered over the distal portion of the cut flap 30, covering theradiopaque marker band 52, to form the distal edge 42 of the flap 30.The small tab 70 and rectangular body 68 extend, by abutting edges, notoverlapping, the proximal edge of the cut flap to form the proximal edge44 of the flap 30. The longitudinally extending edge of the body 68forms the free edge 46 of the flap 30.

Advantageously, the extended overlap 60 provides a larger expanse in thecircumferential direction for the flap 30 to extend over the secondlongitudinal edge 36 (formed by crease 22) of the first circumferentialportion 24 and thus cover the gap formed by cutting the flap from thesecond circumferential portion 26. This extends the reach of the flap 30allowing for its greater movement relative the first circumferentialportion 24 during expansion of the inner member 20, as shown in FIG. 6.Also, the flap 30 is extended in the proximal, axial direction over thedistal cut edge 58 of the second circumferential portion 26.

An additional bilayer tab 80 can be tacked to the proximal edge of thecut flap 30 and circumferentially adjacent to the free end of the smalltab 70. In FIG. 6, for example, the bilayer tab 80 has an axiallyextending edge 81 bonded to and extending circumferentially away fromthe top or free edge of small tab 70. The bilayer tab 80 also has adistal edge 83 bonded to the proximal edge of the cut tab 30. Thebilayer tab 80 is also at least partially bonded to the outer surface ofthe underlying first circumferential portion 24. The bilayer tab 80 hasan elastomeric composition that, because it is bonded to and connectsthe more stiff first circumferential portion 24 and flap 30 and flapextension 60, facilitate a smooth transition between the cut flap andthe inner member 20 at the adjacent first and second circumferentialportions 24, 26. The bilayer tab 80 can have a rectangular shape, suchas a 2 mm by 5 mm rectangle, and a 0.007 inch and 0.012 inch layerthickness. Other shapes, sizes and thicknesses could be applied tomanage the transition between the flap and adjacent inner member,although matching the thickness and using an elastomeric material hasadvantages of improved smoothness and elasticity.

Referring again to FIGS. 8 and 9, the cross-section shows where thelarge tab 72 of the extended overlap 60 (with 0.005 inch thickness) isattached onto the top surface of the underlying first circumferentialportion 24 (with the 0.012 inch thickness) supporting the marker band52. And, as described above, the proximal edge of the bilayer strip 62is tacked to the distal edge of the built-up composite flap 30.Advantageously, the structure described above facilitates a smoothtransition between the flap 30 with the extended overlap 60 and theinner member 20.

As shown in FIG. 9, the outer elastomeric member 50 is then loaded overthe inner member 20 and distal tip 28 structure which are positioned ona mandrel 86. (Formation of proximal portions of the sheath 10,including the wider diameter proximal strain relief end, are shown inthe '109, '111 and '454 applications incorporated herein by reference.)The outer elastomeric member 50 does not extend to the distal edge ofthe bilayer strip 62 to facilitate a taper in the wall thickness of thesheath 10.

On the mandrel 86, the outer elastomeric member 50 is bonded to thebilayer strip 62, and the bilayer strip 62 is completely fused to thedistal edge of the inner member 20, to form the annular structure of theelastomeric free end 54. The mandrel 86 is preferably tapered tofacilitate closing of the overlying gap 84 between the free edges 82 ofthe bilayer strip 62 and formation of the smoothly taperingfrusto-conical shape of the distal tip of the sheath (shown in FIG. 2)during bonding.

Some portion of the thinner outer layer 64 of the bilayer strip 62, suchas about an additional 0.5 mm to 1 mm, can extend axially beyond thedistal end of the outer elastomeric member 50. This additional portionof the outer layer 64 is shaped by heat and the underlying mandrel 86for an even more progressive tapering of the free end 54 wall thickness.Additionally, after bonding the bilayer strip 62, the process caninclude cutting through the bilayer and outer elastomeric member 50 atthe elastomeric free end 54. Cutting through the free end wall creates agap similar to the gap 84. Then the free end 54 can be rebounded usingthe mandrel 86. Advantageously, the cutting and re-bonding processselectively weakens the elastomeric free end 54 to open more easilyduring passage of an implant. This facilitates easier deployment and/orretrieval through the tip.

Advantageously, the tip and folding structure allows for a largedifference between the expanded and nonexpanded diameters of the sheath10. For example, the resulting final outside diameter of the sheath 10can be as small as 19±1 French while the unfolded inside diameter is 14French depending on the selected material wall thickness. Otheradvantages provided by the structure of the distal tip 28 include a moreregular shape, reduced tip profile and a smoother tip transition. Also,the fewer layers and elastomeric free end 54 help to reduce push forcethrough the tip. Formation and extension of the flap 30 opens up theinner member 20 and facilitates opening of the tip to greater diametersthan the proximal end of the inner member, for example 30% or greaterexpansion over the folded diameter. This lowers forces and improvesreliability of balloon, valve and other implant retrieval.

FIG. 12 shows the smooth transition of the distal tip 28—with a steadilydecreasing diameter—to the final diameter of the distal-most edge of thesheath 10. FIG. 13 shows also the relatively small step down from thedistal end of the sheath 10 to the mandrel 86. Thus, the distal tip 28can provide much greater expansion capability without a substantialincrease in step height, angle of taper or outer diameter at the end ofthe sheath 10.

Various embodiments of the distal tip 28 include various advantages,such as elimination of splits in the sheath, lifting of the folding edgeand tip delamination. Also, the distal tip 28 can better receive alarger deflated balloon profile for the retrieval of the deliverysystem. Further, the distal tip 28 can provide an improved tip profile,recovery capability, and circularity during recovery. Tip transitionsmoothness is improved, as well as push forces reduced and made moreconsistent, by embodiments of the distal tip 28.

In another embodiment, the expandable introducer sheath 10 can include aproximal hemostasis seal assembly 88, as shown in FIGS. 14, 22A and 22B.The proximal positioning of the seal assembly 88—away from the distaltip of the expandable sheath 10—reduces the size of the distal tip,smooths the profile of the distal tip and allows the flap 30 to slidemore freely than if it were sealed. The proximal seal assembly 88 isparticularly advantageous when used with the flap assembly 30 becausethe flap assembly's structure can allow invasion of fluids from thepatient between the layers of the sheath 10.

The proximal seal assembly 88, for example, can include a middle member90 that extends from an inner surface 92 of the outer elastomeric member50 to an outer surface 94 of the inner member 20. As shown schematicallyin FIG. 14, the middle member 90 has an expanded, open distal end 96with an outer surface that is connected to the inner surface 92 of theouter elastomeric member 50, such as by tacking or bonding. The middlemember 90 tapers in the proximal direction to an annular attachment tothe outside surface 94 of the inner elongate member 20.

The open distal end 96 of the proximal seal assembly 88 is not connectedto the inner member 20 of the sheath 10 and can receive fluid from aleak path 98 between the members 20, 50, as shown in FIG. 17. The leakpath 98 extends, therefore, between the inner surface 92 of the outerelastic member 50 and the outer surface 94 of the inner member 20. Theleak path 98 can include the space between the overlapping edges 36, 38of the first circumferential portion 24 up to the proximal attachment ofthe middle member 90 to the inner member 20. The leak path 98 extendsfrom the free edges of the inner member 20 and elastomeric member 50where they are unconnected to each other and proximally to theattachment of the middle member 90 to the inner member at a closedproximal end 104, as shown in FIG. 22A.

Stated differently, the unconnected or unattached length extends distalto the middle member's 90 attachment to the inner member 20 to the free,unattached edges of the inner member 20, outer elastomeric member 50 andany other layers or members not attached to each other and therebyallowing full or partial invasion of fluid in a leak path. As shown inFIG. 22B, the leak path 98 can cause some ballooning effects to theportions of the outer elastic member 50 outside the body since it allowsblood pressure to reach the outer elastomeric member 50 (withoutcountervailing body fluid pressure forces to offset the blood pressure).Although not entirely deleterious, ballooning should be curbed oravoided to minimize the chance of leaks.

Although the illustrated leak path 98 has the above-describedcharacteristics, it should be noted that the seal assembly 88 could beemployed without any leak path or the leak path could be different thanbetween the two members 20, 50. Leaks can also occur due to tearing orpin holes forming under arterial blood pressure to the elastomericmember 50 and be managed by the proximal seal assembly. Generally, themiddle member 90 is shown as a tubular member with distal and proximalcylindrical portions connected by a tapering conical region in themiddle. It should be noted, however, that the seal assembly 88 could beconstructed of a range of materials, layers and members and achieve theend of mediating proximal migration of leaks. For example, a disc-shapedplug can be employed that extends between the inner surface 92 and outersurface 94 so as to block the leak path. Or, multiple layers could beused, employing several of the middle members in combination with plugs.Or, as another example, a duckbill style valve could be employed tomaintain some movability in the axial direction between the members 20,50.

The proximal positioning of the proximal seal assembly 88 is generallymore proximal than the distal tip 28 including the flap 30. In theillustrated embodiment, the proximal seal assembly 88 is adjacent to orslightly distal to a strain relief portion 100 of the sheath, as shownin FIG. 14. In any case, generally, the more proximal the positioning ofthe proximal seal assembly 88, the easier it is to operate theexpandable introducer sheath 10 because a bump, irregularity orthickening due to the seal is present only for a short insertion length(FIG. 22A) or is entirely outside the body, as shown in FIG. 22B. But,at the same time, the more distal the positioning of the proximal sealassembly 88, the better it is suited for positioning at or just insidethe percutaneous opening 200 in the body, as shown in FIG. 22A. Withsuch positioning, any ballooning (FIG. 22B) that can arise from theblood pressure in the leak path 98 exerting expansion forces on theelastic outer elastomeric member 50 can be reduced, minimized oreliminated. In embodiments used for femoral access to the aortic valve,the proximal seal assembly 88 can be located 9.5 cm or further from thehousing at the proximal end of the device and about at the end of thestrain relief portion 100.

As shown in FIG. 14, the expandable sheath 10 can also include a fusedportion 105. In particular, the fused portion 105 is where theelastomeric member 50 has been fused or attached to the inner member 20.The fused portion 105 starts at and extends proximally from the closedproximal end 104 of the seal. As shown in FIG. 20, this fusion allowsthe outer elastomeric member 50 to fold along with the inner member 20into the folded configuration and further blocks against leakage betweenthe members 20, 50. The seal assembly 88 can also include an outerjacket 102 that has a tubular shape and extends along an axial portionof the sheath 10 overlapping the middle member 90 of the seal. The outerjacket 102 is preferably of an elastomeric material and is used to urgethe fused portions of the inner member 20 and outer elastomeric member50 into the collapsed configuration and to urge blood out between themembers at the open distal end 96. Further, the outer jacket 102 caninclude a marker to indicate the depth at which the user can advance thesheath 10 to minimize or eliminate ballooning.

Generally, FIGS. 15-21 illustrate a proximal seal manufacturing process.In FIG. 15, an inner member 20 is extruded or otherwise providedincluding the first and second circumferential portions 24, 26. In FIG.16, the inner member 20 is conditioned via repeated folding into thefolded or compressed configuration. In FIG. 17, the elastomeric outerlayer 50 is sleeved over the outside surface of the inner member 20 inits folded configuration. In FIG. 18, the inner member 20 is opened intothe unfolded configuration through insertion of a mandrel 86 into thelumen of the inner member. The outer elastomeric member 50 is alsoexpanded (stretched) against its elastomeric bias into the expanded,unfolded configuration.

In FIG. 19, the outer elastomeric member 50 is fused to the outsidesurface of the inner member 20 (at least at the proximal seal assembly88 location). FIG. 20 shows the fused assembly being folded—includingthe outer elastomeric member 50—into the folded configuration andincludes the addition of an elastomeric outer jacket 102. FIG. 21 showsthe fused assembly in an expanded configuration. Notably, the closedproximal end 104 of the seal 88 could also be formed by fusing themiddle member 90 to the inner member 20 to form the closed proximal end104 and fusing the middle member 90 to the outer elastomeric member 50to form the open distal end 96. In any case, the leak path 98 is sealedat least partially against proximal migration of fluids.

The outer jacket 102 can be configured to give a visual indicator ofwhen the valve assembly 88 has been advanced close or into the patientto guard against leakage and/or to provide additional restraint againstballooning of the outer elastomeric member 50 around the leak path. Forexample, the outer jacket 102 can be constructed of a NEUSoft band thatis then pen or cold laser marked to illustrate the depth at which thesheath 10 is advanced within the patient's body. The axial length of theouter jacket for example can be 1⅛ inch with the seal length being ⅝inch. A distal portion of the outer jacket 102 can extend, for example,⅛ inch further than the distal end of the seal assembly 88 while anadditional ⅜ inch is present on the proximal end of the seal assembly 88for some safety margin.

As described above, the expandable sheath 10 can be used to deliver,remove, repair, and/or replace a prosthetic device. In one example, thesheath 10 described above can be used to deliver a prosthetic heartvalve to a patient. For example, after the sheath 10 is inserted intothe body and into the patent's vasculature, a heart valve (in a crimpedor compressed state) mounted on the distal end portion of an elongateddelivery catheter is inserted into the sheath. Next, the deliverycatheter and heart valve can be advanced through the sheath and throughthe patient's vasculature to the treatment site, where the valve isimplanted.

In particular, when the sheath 10 is used to deliver the implant, theflap 30 of the distal tip 28 expands to a much larger diameter than justunfolding the elongate inner member 20 for easy deployment and retrievalof balloons and implants. As the implant is passed through the distaltip 28, the free edge 46 of the flap 30 rides up the outside surface(under outer elastomeric member 50) to expand the space in the tip. Theelastomeric free end 54 also expands to accommodate the implant. Thedistal tip 28 can expand again during retrieval of the delivery deviceor retrieved implant, with the flap 30 once again sliding freely at theproximal, distal and free edges 42, 44 and 46 to easily receive thedeflated balloon or retrieved implant.

Further, while the expandable sheath 10 is advanced in the high pressureof the patient's arteries, the blood extends into the leak path 98 butis blocked by the seal assembly 88. As shown in FIGS. 22A and 22B, thesheath 10 is advanced until the outer jacket 102 abuts or extends intothe inside of the patient's body. This reduces or eliminates ballooningof the outer elastomeric member 50 due to the pressure of the blood orother body fluids.

Beyond transcatheter heart valves, the expandable sheath 10 can beuseful for other types of minimally invasive procedure, such as anyprocedure requiring introduction of an apparatus into a subject'svessel. For example, the expandable sheath 10 can be used to introduceother types of delivery apparatus for placing various types ofintraluminal devices (e.g., stents, stented grafts, balloon cathetersfor angioplasty procedures, etc.) into many types of vascular andnon-vascular body lumens (e.g., veins, arteries, esophagus, ducts of thebiliary tree, intestine, urethra, fallopian tube, other endocrine orexocrine ducts, etc.).

Although the foregoing embodiments of the present disclosure have beendescribed in some detail by way of illustration and example for purposesof clarity and understanding, it will be apparent to those skilled inthe art that certain changes and modifications may be practiced withinthe spirit and scope of the present disclosure. It is intended that thescope of the present invention herein disclosed should not be limited bythe particular disclosed embodiments described above, but should bedetermined only by a fair reading of the claims that follow.

What is claimed is:
 1. An expandable sheath comprising: an elongatedinner member including at least one foldable axial portion; an outerelastomeric member extending at least partially over the inner memberand configured to exert a compressive force onto the inner member tobias the at least one foldable axial portion into a foldedconfiguration; and a proximal seal including a middle member extendingfrom an outer surface of the inner member to an inner surface of theouter elastomeric member, the seal configured to guard against proximalmigration of fluid from a distal free end of the expandable sheath to aproximal end of the expandable sheath.
 2. The expandable sheath of claim1, wherein the inner member and outer elastomeric member have anunconnected length distal to the proximal seal.
 3. The expandable sheathof claim 2, wherein the unconnected length extends distally from theproximal seal to the distal free end of the expandable sheath.
 4. Theexpandable sheath of claim 3, wherein the proximal seal is configured toblock a path starting at the distal free end and extending proximally tothe proximal seal.
 5. The expandable sheath of claim 1, furthercomprising an outer jacket extending over the outer elastomeric memberat the proximal seal.
 6. The expandable sheath of claim 1, wherein theouter elastomeric member is fused to the inner member at the seal. 7.The expandable sheath of claim 6, wherein the outer elastomeric memberis foldable at the proximal seal along with the inner member.
 8. Theexpandable sheath of claim 7, wherein the inner member is foldableindependent of the outer elastomeric member distal to the seal.
 9. Theexpandable sheath of claim 8, wherein the elongated inner member isconfigured to at least partially unfold to an open configuration forpassage of an implant.
 10. The expandable sheath of claim 1, furthercomprising a strain relief portion extending distally from the proximalend of the expandable sheath and wherein the proximal seal has aproximal end adjacent a distal end of the strain relief portion.
 11. Theexpandable sheath of claim 1, wherein the elongated inner member definesa central lumen, a first circumferential portion including first andsecond longitudinal edges, and a second circumferential portionextending between the first and second longitudinal edges.
 12. Theexpandable sheath of claim 11, wherein the elongated inner member isconfigured to crease at the first and second longitudinal edges into thefolded configuration wherein the second circumferential portion ispositioned at least partially between the overlapping longitudinaledges.
 13. The expandable sheath of claim 12, wherein the elongatedinner member further includes a distal tip, the distal tip including aflap extending from the first longitudinal edge and at least to thesecond longitudinal edge in an open configuration of the elongated innermember.
 14. An expandable sheath comprising: an elongated inner memberdefining a central lumen, a first circumferential portion including afirst and second longitudinal edges, and a second circumferentialportion extending between the first and second longitudinal edges,wherein the elongated inner member is configured to crease at the firstand second longitudinal edges into a folded configuration wherein thesecond circumferential portion is positioned at least partially betweenthe overlapping longitudinal edges; and an outer elastomeric memberextending around the elongated inner member and configured to bias theelongated inner member into the folded configuration; wherein theelongated inner member further includes a distal tip, the distal tipincluding a flap extending from the first longitudinal edge and at leastto the second longitudinal edge in an open configuration of theelongated inner member.
 15. The expandable sheath of claim 14, whereinthe flap is configured to slide circumferentially over an outer surfaceof the first circumferential portion when the elongated inner member isbiased into the folded configuration by the elastic outer member. 16.The expandable sheath of claim 14, wherein the second circumferentialportion has a distal edge extending longitudinally at least to aproximal edge of the flap.
 17. The expandable sheath of claim 16,wherein the proximal edge of the flap extends over the distal edge ofthe second circumferential portion onto an outer surface of the secondcircumferential portion.
 18. The expandable sheath of claim 14, whereinthe flap includes a longitudinal section of the second circumferentialportion cut along the second longitudinal edge.
 19. The expandablesheath of claim 18, wherein the longitudinal section is also cutcircumferentially from the distal end of the second circumferentialportion.
 20. The expandable sheath of claim 14, wherein the flap furtherincludes an overlap extension that extends circumferentially from thelongitudinal section.
 21. The expandable sheath of claim 20, wherein theoverlap extension extends proximally from the longitudinal section. 22.The expandable sheath of claim 14, wherein the distal tip furthercomprises an elastomeric end extending from a distal end of theelongated inner member.
 23. The expandable sheath of claim 22, whereinthe elastomeric end has a distally tapering shape.
 24. The expandablesheath of claim 14, further comprising a marker embedded in the distaltip of the elongate inner member.